M4.7 earthquake 43 km WSW of Santa Cruz, Chile

Saturday, April 2, 2011, 16:26:51 UTC · 34.735°S, 71.821°W

A magnitude 4.7 earthquake struck 43 km WSW of Santa Cruz, Chile on Saturday, April 2, 2011, 16:26:51 UTC, at a depth of 43.5 km (shallow). USGS received 9 “Did You Feel It?” reports, with a maximum reported intensity of IV (light). It is the strongest earthquake within 300 km since an M4.8 on April 2, 2011.

Magnitude: 4.7; Light · mb
Depth: 44 km; Shallow
Felt reports: 9; Max intensity IV
Est. shaking: —; No ShakeMap
PAGER alert: None; Not issued
Tsunami: No flag; USGS feed

Outlined circle: this earthquakeDashed circle: 50 km aftershock search area

In context

How big was it, and why here?

Energy released

169 tons of TNT

That is about 1/89 of the Hiroshima bomb. A magnitude 5.0 releases about 3 times more energy.

Tectonic setting

138 km

from the nearest mapped plate boundary, between the Nazca and South American plates. Earthquakes this far from a boundary happen on faults inside a plate, often less frequently but sometimes strongly.

Depth: shallow

44 km

Shallow earthquakes (under 70 km) produce the strongest surface shaking for their size, so they are the ones most likely to cause damage near the epicenter.

Did You Feel It?

Where it was felt

Reports sent by people to USGS, grouped by place (most reports first). Intensity uses the Modified Mercalli scale (I–X): what people felt, not the magnitude.

Place	Intensity	Reports	Distance
Santiago, Metropolitana, Chile	II · Weak	4	183 km
San Vicente, Libertador General Bernardo OʿHiggins, Chile	IV · Light	1	87 km
Machalí, Libertador General Bernardo OʿHiggins, Chile	III · Weak	1	129 km
Talca, Maule, Chile	II · Weak	1	88 km
Rengo, Libertador General Bernardo OʿHiggins, Chile	II · Weak	1	103 km
San Antonio, Valparaíso, Chile	II · Weak	1	134 km

I felt it — report to USGS ↗

USGS PAGER estimate

Who was exposed to shaking

USGS publishes PAGER impact estimates for significant earthquakes, usually within an hour. No PAGER estimate is available for this event.

After the main event

Aftershocks within 50 km

USGS lists 6 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M4.5 on April 22, 2011. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.

Regional history

Past M5+ earthquakes within 300 km

USGS lists 691 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 43 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 35,721 recorded deaths. The most severe:

1939M8.3
Chillan
25 Jan 1939 · 173 km away · intensity X
30,000 deaths$920 million damagetsunami
1906M8.2
South Central
17 Aug 1906 · 194 km away · intensity XI
4,000 deaths$100 million damagetsunami
2010M8.8
Maule, Concepcion, Talcahuano
27 Feb 2010 · 183 km away · intensity IX
558 deaths$30 billion damagetsunami
1965M7.3
Central
28 Mar 1965 · 266 km away
400 deaths$125 million damage
1928M7.6
Talca, Chillan, Santiago, San Fernando
1 Dec 1928 · 34 km away · intensity IX
279 deathsSevere damage ($5–24M)tsunami
1985M8.0
Central Coast, San Antonio, Valparaiso
3 Mar 1985 · 179 km away · intensity VIII
180 deaths$1.5 billion damagetsunami

NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.

Nearby trackers